Vibratory conveyors



Sept. 6, 1960 Original Filed Jan. 5, 1953 G. LONG ETAL VIBRATORYCONVEYORS FIG.|

2 Sheets-Sheet 1 so i.

INVENTORS' GEORGE LONG TAKUZO TSUCHIYA 9; Carmen) Patented Sept. 6, 1960VIBRATORY CONVEYORS George Long and Takuzo Tsuchiya, Minneapolis, Minn.,

assignors to General Mills, Inc., a corporation of Delaware'Continuation of application 'Ser. No. 329,556, Jan. 5, 1953. Thisapplication June 9, 1959, Ser. No. 819,085

8 Claims. (Cl. 198-220) The present invention relates to vibratoryconveyors and more particularly to vibratory conveyors in which thetransmission of undesired forces to any stationary support or buildingis eifectively minimized. This dis closure is a continuation of ourco-pending application U.S. Serial No. 329,556, filed January 5, 1953,now abandoned.

Vibratory conveyors are well known in which a conveying member isconnected to a building or other stationary support by means of inclinedsprings. Cyclical or vibratory forces of various types have then beenapplied to the conveying member to cause it to vibrate back and forthalong an inclined arcuate path generally perpendicular to the springsandthus convey material across the member. In some cases, the desiredforces have been applied by a rotating unbalanced weight on theconveying member, while in other cases, the forces have been applied bymeans of a source of power mounted on the stationary support or buildingand connected to the conveyor either by a rigid crank or eccentricarrangement or by some magnetic force transmission device.

In these prior cases, the application of the desired force impulses tothe conveying member has resulted in the transmission of equal andopposite forces to the stationary support or building. In many conveyingapplications, the magnitude of these forces has been so great thatdamage to the supporting structure or building would result unless thestrength and mass of the supporting structure were increasedsubstantially. Thus for such applications, the ordinary type ofvibratory conveyor has been either too costly or impractical to justifyits use, and other means of handling materials have had to be sought.

Various attempts have been made to avoid the transmission of suchvibrations to the supporting structure. For example, some priorconveyors utilize a counterbalancing mass which is attached to theconveying memher in such a way that the counter-balancing masssupposedly balances the vibrations of the conveying member. Thisincreases the proportion of non-useful non-working weight of thestructures which must be paid for by the purchaser. To be economical,the proportion of nonuseful material in the structure should be at aminimum.

In other cases, self-contained force applying members such as rotatingeccentric weights have been mounted directly on the work performingmember. Here, however, the vibrations of the. working member causeuneven and excessive wear on the shafts and bearings of the eccentricweight device.

Another attempt to avoid the transmission of undesired vibrating forcesor motions has involved the provision of an additional resilient orspring support between a base member which carries the inclined springsof the conveying unit and the foundation or building on which suchsprings would otherwise be mounted. These intermediate cushioningsprings have, however, been designated as soft or coil springs, and havebeen intended to provide a floating or resilient support with nospecific rigidity. In some cases, the mass of the base member is madevery large to minimize such forces and motions.

In one arrangement, involving coil springs for floating support of theintermediate base, it has been further suggested that the necessaryconveying forces can be applied by means of a single rotating unbalancedweight mounted on the intermediate base member rather than on theconveying member. The theory of this suggestion has been that motion ofthe intermediate base could be reduced to zero at certain frequencies.As pointed out in detail below, however, we have found that the use ofsuch a rotating weight on the intermediate base, in combination withsoft or coil springs for support, of the intermediate base, not onlyfails to keep the intermediate base completely stationary, but mayinvolve both a vertical and a rocking action of the intermediate base.This rocking action was found to produce undesired movements of theconveying member which were not the same at all points along the lengthof the conveying member and which could seriously interfere with orcompletely prevent the desired lateral movement of material on theconveyor.

With the above problems and difliculties of the prior art in view, oneobject of the present invention is the provision of an improvedvibratory conveyor in which the transmission of undesired force impulsesto a stationary support or building is kept as small as possible withoutadverse effect on the desired conveying action.

A further object is the provision of a vibratory conveyor in which aconveying member is connected to an intermediate base member by inclinedspring beams, and in which the-desired conveying forces are obtained byapplication of appropriate cyclical or vibratory forces to theintermediate base member alone.

Still another object is such a vibratory conveyor in which theintermediate base member is in turn supported by spring beams from asuitable stationary support, in such a way as to insure elfectiveoperation of the conveying member. a

A still further object is a vibratory conveyor of the above type inwhich reciprocating forces are applied to the intermediate base memberin a direction which minimizes force transmission to the support.

Another object is the provision of a vibratory conveyor in which a firstset of spring beams provides the sole supporting connection between aconveying member and a suitable intermediate base, while a second set ofspring beams provides the sole connection between the intermediate baseand a stationary support.

Another object is the provision of a vibratory conveyor of this typewith preferred relative locations and orientations of the two sets ofspring beams.

Other objects and advantages of the invention will be apparent from thefollowing description in which certain preferred embodiments of theinvention are disclosed.

In the drawings which accompany this application and in which likereference characters indicate like parts,

Figure l is a perspective view of one form of vibratory conveyoraccording to the present invention.

Fig. 2 is a schematic diagram of the device of Fig. 1 in side elevation.

Fig. 3 is a view similar to Fig. 2 of a preferred form of vibratoryconveyor according to the invention.

Fig. 4 is a similar schematic view of another form of the presentinvention.

Fig. 5 is a similar schematic view of another modification designedtominimize the transmission of undesired torques to the foundation.

Fig. 6 is a view of a modification in which the conveyor andintermediate base are mounted from an overhead support.

Fig. 7 shows a modified arrangement with an overhead support, and with apreferred orientation of reciprocatory force applying means.

Figs. 8 and 9 are schematic views of prior art constructions, which areincluded in order to facilitate understanding of the novel and inventivefeatures claimed herein, and' Fig. 10 is a sectional view on line 10-10of Fig. 7.

As illustrated specifically in Figs. 1 and 2, the present inventionincludes a conveying member 10 adapted to convey material from an inletend at 12 to an outlet end at 14. This conveying member 10 is generallyhorizontal, although it may obviously be inclined somewhat uphill ordown hill depending on the nature of the material to be conveyed andother requirements and characteristics of a particular installation.

For purposes of illustration, a single longitudinally extending conveyoris shown, which has a straight horizontal direction or path of feed,although certain of the prin ciples of the present invention can beapplied satisfactorily to a conveying member or combination of conveyingmembers which follow other paths, such as circular or helical paths.

An intermediate base member, indicated generally at 16, extendsgenerally parallel to the conveying member 10 and is verticallydisplaced with respect to such conveying member. In this embodiment, theintermediate base 16 is located below the conveying member, although incertain cases as described below it may, for convenience, be locatedabove the conveying member.

The intermediate base member 16 includes longitudinally extending sideframe members 18 and 20 and front and rear cross members 22 and 24.These frame members are connected to each other in such a way as toprovide a substantially rigid intermediate base unit.

To connect the conveying member 10 and base member 16, a first set ofspring beams is provided. In the simple case illustrated, the setincludes two spring beams 26 and 28 which are illustrated in the form offlat or leaf springs. The upper ends of these spring beams are rigidlyclamped to plate-like extensions 32 on tubular conveying member supports34 at points spaced longitudinally along the direction of feed on theconveying member. These supports are clampedto the conveyor tube at 36and serve both to connect the spring beams to the conveying tube 10 andalso to cooperate with the spring beams in providing the sole supportfor the conveying member.

The lower ends of spring beams 26 and 28 are clamped to the intermediatebase member 16 at points 38 and 40, respectively, which are also spacedlongitudinally along the direction of feed. While both ends of thespring beams are shown as rigidly connected in this figure, it is onlynecessary that one end of each spring be rigidly secured, while pivotalconnections could be used at the remaining ends. In such a case,however, four times the number of springs would be needed for the sameresilience, if the spring length remains the same. Thus this first setof spring beams, as pointed out above, provides the sole supporting orweight bearing connection between the conveying member and the basemember. Because the spring beams 26 and 28 are inclined slightly fromthe vertical, and because they are resiliently movable transversely oftheir length, the spring beam connection provides for relative movementof the conveying member along a slightly inclined path which extendslongitudinally of the conveying member and substantially perpendicularlyto the planes of the flat spring beams 26 and 23. The actual path ofrelative movement is more in the nature of an arc, but for smalldisplacements or vibrations along this path, the path may be consideredalmost as a straight 4 line. The actual path of movement is illustratedby the arrow 42 of Fig. 2.

According to an important feature of the present invention, theintermediate base 16 is supported by a second set of spring beams, twoof which are illustrated at 44 and 46 in Fig. l. The lower ends of thesespring beams 44 and 46 are rigidly clamped at 48 and 50, respectively,to a suitable support, such as the rigid plate 52. This plate 52 may inturn be rigidly connected to a larger base member 54 which mayconstitute the floor or frame of the building, or even a separate andessentially portable supporting platform which can be moved from placeto I place with the conveyor unit.

The upper ends of spring beams and 46 are rigidly clamped to theintermediate base member 16 and thus the second set of spring beamsconstitutes the sole supporting connection for this intermediate base,and in turn for the conveying member 10 which is carried by the base.Here again a rigid connection at one end of each spring and a pivotalconnection at the other can be used.

It is important according to the present invention that the springs ofthe second set are substantially n0n-extensible and non-compressible ina lengthwise direction, i.e., lengthwise of the springs. In thisrespect, the spring connection between the intermediate base 16 and thestationary support 52, 54 differs substantially from any of the softcoil springs or other floating supports which have been suggested in theprior art.

In general the spring constant k for the lower springs should be smallto reduce the horizontal forces and to displace the first criticalfrequency of the system toward the lower end of the frequency range.This reduces the chances of undesired vibration as the machine is shutdown and the frequency decreases. In case of large product damping orother damping, a smaller resilience k will reduce the force transmissionto the foundation. At the same time, however, this resilience k of thelower springs must be great enough to support the system as a whole.Within these general principles, the spring constant k should be lessthan the spring constant k for the first set of springs, and preferablyless than one-fourth of the spring constant k while, in general, themasses m and m are of the same order of magnitude.

To obtain the desired relative movement of conveying member 10 along thepath indicated by arrows 42, suitable force impulses are applied to theintermediate base member 16 by a force-applying means indicatedgenerally at 56. This force-applying means is of a type which isessentially self-contained so that the necessary and desired forces areapplied only to intermediate base 16 without the transmission ofopposite reactive forces through the forceapplying means to other partsof the assembly or the foundation on which the assembly is located. InFig. 1, the means for applying cyclical forces to the intermediate basemember 16 is illustrated as a substantially horizontal shaft 58 whichextends transversely of the direction of feed of the conveying member10. It is rotatably supported in the side frame members 18 and 20 of theintermediate base. An eccentric or unbalanced weight 60 is supported onshaft 58 and the shaft is rotated by means of a flexible coupling 62which in turn is driven by the output shaft 64 of a suitable gearbox ortransmission 66,. For greater flexibility of practical adjustment orexperiment, the transmission 66 may be provided with means (not shown)for variation in the speed of output shaft 64. This shaft is suitablygeared to a driving motor 68, and either the motor speed may be variedor the connections between the motor and the output shaft 64 may beadjusted in known manner.

According to the invention, the frequency of the force impulses appliedto the intermediate base 16, which in turn will depend on the rate ofrotation of shaft 58, is adjusted approximately in the range of thenatural frequency of the system which includes the conveying member andthe first set of spring beams 26, 28. This natural frequency is definedby the formula where k is the spring constant of the upper spring means,and m; is the effective mass of the conveying member on such springs.

By operation at exactly this frequency, it is theoretically possible (byignoring frictional or product damping and other factors) to reduce therelative back and forth horizonal movement of the intermediate basemember 16 to zero. In other words, the horizontal components of forceapplied by the eccentric weight 60 (or to be more exact, thosecomponents perpendicular to the upper spring beams 26, 2'8 and parallelto the path of relative movement 42) will be balanced or neutralized inany given instant by equal and opposite forces resulting from therelative deflection of the conveying member 10 and first set of springbeams along said inclined path 42. In this way, forces applied to theintermediate base member 16 result in the desired conveying vibrationsof the conveying member 10 .without substantial horizontal move ment ofthe intermediate base 16. To the extent that this intermediate base 16remains stationary, no longitudinal horizontal force impulses will betransmitted to the foundation by the lower set of spring beams 44 and46, since such springs will remain undeflected.

In actual practice, a system of the type shown in Figs. 1 and 2 involvesnot only the primary forces, such as those applied by the unbalancedrotating weight 60, but involves secondary forces which may beconsidered as of a frictional or damping nature. These additional forceeffects may, in a given case, result in some vibration or reciprocationof the intermediate base 16 andmay require operation of the rotatingunbalanced weight 60 at a frequency slightly different from the aboveso-called natural frequency of the upper portion of the system. Thedirection and extent of this variation in the force frequency can bereadily determined in a given case either by consideration of thetheoretical analysis given below or by simple test in actual operation.

We have stated that is the undamped natural frequency of the m k system.If there were no damping whatsoever, the amplitude of vibration of theintermediate frame would be zero when the forced frequency was madeequal to this undamped natural frequency.

In practice, such an ideal situation is never quite met, since dampingwill always be present to a greater or lesser extent. product load, airresistance or other factors, the vibration of the intermediate framecannot be reduced to zero in all cases.

Yet if the damping is relatively small compared to the critical dampingof the system (i.e., if the so-called dampng constant C is not greaterthan 0.25C Where C critical damping=2Vk m and depending to some extenton the actual ratios of m to m and k to k there will generally be aparticular value or range of values of the forced frequency, in theimmediate vicinity of the undamped natural frequency, atwhich thevibrations of the intermediate base will have a definite minimum. Wehave observed that this particular value of the forced frequency isgenerally different from, and in fact somewhat less than the undampednatural frequency.

On the other hand, if the damping is relatively great compared to thecritical damping, the situation may be quite different and there may beno such well defined minimum. It may even be difificult in such a caseto achieve good conveying action of the working member. The damping wespeak of here is the total damping in Because of this damping, which maybe due to.

the system. This may be considered to include all types of damping aswell as the mass effect of the product being conveyed.

Thus if large values of damping are anticipated, much can be done toimprove the operation and minimize the vibrations of the intermediatebase, the horizontal forces transmitted to the foundation, and the wearand tear on the force applying mechanism, by a careful selection ofdesign parameters. In other words, the adverse effect of damping can bereduced by making the product of k times In as large as possible,consistent with other design conditions, and thus keeping the criticaldamping high as compared to actual damping.

In operation, the vibratory conveyor is first set to operate withoutload, at the undamped natural frequency. The forced frequency is thenadjusted in the neighborhood of this natural frequency with the conveyorunder normal load. The final Working frequency is then chosen on thebasis of the minimum motion of the intermediate base which is consistentwith good conveying action of the working member.

It is important, in any case, that the spring beams 44, 46 of the lowerset have a substantial vertical or longitudinal rigidity, so that theyprevent relative vertical movement of the intermediate base 16 and alsoresist any rocking motion of the intermediate base which might otherwisetend to result due to a couple which is set up between the cyclicalforce of the unbalanced weight 60 and the inertial reaction of theconveyor. This couple is shown in Fig. 2 with the forces acting at adistance x apart, and is discussed further below in connection with Fig.9. To resist such. rocking movement the spring beams 44 and 46 aresubstantially non-extensible and noncompressible along their length, andthe spring beams are further oriented in such a way that they extendfrom the intermediate base member 16 in a direction having a majorvertical component.

Another requirement of the supporting spring system 44, 46 is that itprovides the required degree of freedom of movement of the intermediatebase 16 in a direction perpendicular to the upper set of spring beams 26and 28, i.e., parallel to the path of vibrations 42. Ideally, thisdegree of freedom could be supplied by having the spring beams 44 and 46essentially parallel to the upper,

spring beams 26 and 28 as in certain of the modifications describedbelow.

If the angle between the two sets of spring beams increases from zerodegrees or degrees (the parallel condition), it is apparent that theintermediate base 16 becomes less and less likely to remain stationaryduring operation and more and more likely to transmit to the foundationsome of the forces perpendicular to the upper springs. Or to put thematter another Way, the particular arrangement described above tends tobalance and minimize forces perpendicular to the upper set of springbeams 26, 28 because both the upper conveyor member 19 and theintermediate base 16 have relative freedom of mzovement in this samedirection, i.e., parallel to the path 4 Therefore it is important thatthe lower set of spring beams 44 and 46 extend from the intermediatebase 16 in a direction which has a major component parallel to the upperset of spring beams 26 and 28. By the term major component, in thesecases, we mean that the longitudinal direction of the spring beams 44and 46 should not be more than 45 degrees from either the vertical, orfrom a line parallel to the upper inclined springs 26 and 28.

Another way to state this limitation in the orientation of the lowerspring beams 44 and 46 is to consider that orientation of the lowersprings parallel to the upper ones in effect gives the ideal freedom ofmovement to the intermediate base, while orientation of these lowerspring beams in an exactly vertical direction oifers advantages in thevertical support of the intermediate base and its associatedconveyingmember. Thus the preferred range of orientation for the lower springbeams is the range which is limited on the one hand by substantiallyvertical planes normal, to the direction of feed of the conveying member10, and on the other hand by inclined planes parallel to the inclinedsprings 26 and 28 of the upper set.

Aspointed out in the introductory portions of this specification, therehave been some suggestions in the prior art of the possibility ofoperation of a vibratory member in such a way as to' eliminate orminimize transmission of forces to a supporting structure. These priorsuggestions have apparently been based on either practical ortheoretical analysis of systems with only one assumed degree of freedom.In such systems, as illlustrated ghematically in Fig. 8, for example, itis theoretically possible to use the principle of the dynamic vibrationabsorber in such a way that the vibration absorber becomes thework-performing member, and the member whose vibrations are absorbedbecomes the intermediate base which supports the work-performing member.

Thus in Fig. 8', the vertically movable screen 70 is supported byhorizontally and vertically resilient springs 72 on'an intermediate basemember 74. This intermediate base member, in turn, is supported byvertically resilient spring members 76 from a suitable support orfoundation 78. A shaft 86, rotatably mounted on the intermediate base74, carries an unbalanced weight 82 and rotates as indicated by thearrow in Fig. 8 to provide the desired cyclical forces.

'It has "been suggested that such a system can be utilized to providevertical reciprocation of the screen member 70 without substantialmovement of the intermediate base 74, so that, in theory, the lattertransmits no force impulses to the foundation 78 via springs 76.(Actually, as pointed out below, the horizontal forces of the unbalancedweight should not be ignored.)

Based on this theoretical consideration, the prior art then includes atleast one further suggestion for use of a two-mass, two-spring system ofthis type for conveying purposes as illustrated by Fig. 9. Here an upperconveying member 84 is supported on an intermediate base I member 86 bymeans of inclined springs 88 rather than coil springs. The intermediatebase member 86 is then supported by coil springs which provide a softerfloating spring effect at 90. A rotating shaft 92 on the intermediatebase 86 and an unbalanced weight 94 carried by the shaft and rotated ata frequency equal to the natural frequency of the conveyor member 84 onits springs 88 is then said to result in the desired conveying action.

In attempts to follow this prior art suggestion, however, we have foundthat intermediate base member 86 not only fails to remain quiescent assuggested by the theoretical analysis referred to in connection withFig. 8, but that the movements of the intermediate base member 86 areeven such as to prevent any conveying action in the conveying member'84.

We have found that this lack of satisfactory operation of the prior artsuggestions can be avoided by use of the specific structural featuresand combinations described and claimed herein, and particularly by theuse of longitudinally non-extensible or compressible spring beams ofspecific orientation for the support of the intermediate base member.

It is our belief that'the major difficulties which, as far as we know,have prevented the actual manufacture and use of any successfulcommercial conveyor constructed along the prior art lines illustrated inFig. 9 have been the failure to understand that the change fromvertically movable springs as in Fig. 8 to inclined springs as in Fig. 9introduces forces and reactions which yield unobvious torque effects,and the failure to take account of all the forces applied by a singlerotating unbalanced weight. As long as the parts are vertically movableand vertically aligned as in Fig. 8, such effects do not adverselyaffect the vertical movement of the member 70 so as to interfere with ascreening action or a packing or compacting action or something whichdepends upon vertical movement alone.

Introduction of the inclined springs 88 as in Fig. 9, however, yields asystem which is not equivalent to that of Fig. 8 and can not be treatedby the same simplified theoretical'or mathematical approach. Asillustrated in Fig. 9, if relative movement of the intermediate base 86is to be substantially neutralized in a direction perpendicular tosprings 88, then the force indicated by the arrow -P due to theunbalanced weight 94 at a particular instant must be neutralized oroffset by an equal and opposite force shown by arrow P, representing theinertial reaction of the conveyor.

While these forces are equal and opposite, they are not in alignmentwith each other, since they occur at opposite ends of the upper springsystem and at substantially right angles thereto. Thus a rotary ortorque effect is produced which can be said to have a magnitude equal tothe product of P times 1, where 1 represents the perpendicular distancebetween the opposed forces P and P in Fig. 9. For the particular instantillustrated in the figure, this couple produces a torque tending torotate the two-mass system which includes conveyor 84', intermediatebase 86, and springs 88. This'torque will accordingly tend to depressone end of the intermediate base 86 as shown by arrow 96 and to lift theopposite end as shown by arrow 98. \Vhen the weight rotates 180 degreesfarther, the direction of this couple and of the rocking tendency onbase 85 will be reversed. This rocking of base 86 may actually preventconveying of the stock by member 84, or may result in conveying indifferent directions at different areas of the conveying member due tothe non-uniform movement of the conveying member and depending on therelative magnitude of the couple.

We have accordingly found that it is more important, if satisfactoryconveying is to be achieved, to prevent vertical rocking of theintermediate base than to achieve the complete floating effect of thecoil or soft springs required by the prior art. Thus the use of thespring beams as illustrated schematically in Fig. 2 of the presentinvention prevents rocking of the intermediate base 16, while at thesame time the spring beams provide the necessary freedom of movement ina horizontal direction, i.e., in a direction having a major componentperpendicular to the first set of spring beams 26 and 28. This freedomof movement, combined with application of force impulses at or near thespecified natural frequency of the conveying member and first set ofspring beams, makes it theoretically possible to eliminate completely(and actually possible to minimize effectively) the horizontal movementof intermediate base 16. Thus the transmission of horizontal forces tothe foundation or support is reduced to an absolute minimum.

With reference to Fig. 8 again, certain prior art analyses of this typeof system have also failed to take into account the problem of unwantedforce impulses in directions other than those along the vertical path ofmovement of the work member such as screen 70. Thus in connection withFig. 8 it is said that the intermediate base 74 remains stationary atcertain frequencies for the unbalanced. weight 82. In actual practice,however, any balancing of the force impulses from the rotating weight bythe inertial reaction of member and its spring 72 would be essentiallylimited to a vertical direction. Thus the horizontal components of forceapplied by weight 82 wouldnot be particularly neutralized in Fig. 8 andwould cause horizontal deflections of the intermediate base 74 withpossible adverse effects on the desired movement of the work member 70.Thus this prior art arrangement has not provided a means forneutralizing or minimizing the undesired movements of the intermediatebase in a direction substantially at right angles to the path ofmovement of the working member.

In the present case, where the conveying movements involve a path whichis basically horizontal but necessarily includes a substantial verticalcomponent, we have provided a preferred arrangement for the effectiveelimination of the undesired force impulses at right angles to the pathof movement of the conveying member. One form of this preferredarrangement is illustrated in Fig. 3.

Here the conveying member 100 is connected to an intermediate basemember 102 by inclined spring beams 104 similar to the first set ofspring beams previously discussed. The intermediate base 102 is in turnprovided with substantially vertical spring beams 106 which provide thesole supporting connection between the intermediate base and astationary support or foundation 108.

In this case, the desired force impulses are of a reciprocating natureand are provided by balanced counterrotating weights 110 and 112 carriedbyshafts 114 and 116, respectively. These shafts rotate in oppositedirections from the position illustrated in Fig. 3, so that all forcesof the two equal and opposed weights are cancelled out at any giveninstant except those forces along a line perpendicular to the commonplane of the two parallel shafts 114 and 116. These forces are indicatedby the arrows 118. The shafts 114 and 116 are rotatably mounted onintermediate base 102 and may be driven in known manner e.g. by aseparate motor and flexible shaft connection as in Fig. 1, or by asuitably oriented belt connection as in Fig. 7. The shafts areinterconnected by gearing in a manner equivalent to that shown in thedevice of Figs. 7 and 10.

In Fig. 3, the parts are so oriented that the common plane of the shafts114 and 116 is parallel to the upper set of spring beams 104 and thusthe force impulses are of a reciprocating nature along a lineperpendicular to the upper spring beams. Thus these forces can beneutralized by the opposed forces due to inertial reaction of theconveyor 100 on the upper end of springs 104. In this case substantiallythe only forces transmitted to the foundation 108 through springs 106will be the alternating torques resulting from the couple formed by theforceapplying member on the one hand and the inertial reaction of theconveyor 100 on the other, together with such secondary verticalaccelerationsas may be attributed to product damping due to the actualload carried on the conveying member 100.

While it is theoretically best from the standpoint of balancing outundesired forces and motions to apply the reciprocatory forces along aline perpendicular to the first set of spring beams, we have foundthatthere are practical reasons which lead to a different arrangement inmany cases. For example, the inclination of the path of thereciprocating forces along a line perpendicular to the upper inclinedsprings produces an arrangement in which such forces have verticalcomponents perpendicular to the intermediate base. If this intermediatebase is not sufliciently rigid, or if it is relatively long compared toits vertical thickness, these vertical components may flex theintermediate base up and down and cause undesired forces and motions.

To avoid such problems, and because it is easier to make theintermediate base longitudinally rigid than laterally inflexible, weprefer in most cases to apply the reciprocating forces along a lineparallel to the inter mediate base. Thus the reciprocating forces areapplied in a longitudinal direction, within the range bounded by linesperpendicular to the first set of spring beams and lines parallel to theintermediate base, and preferably nearer the latter. Also, to avoiduneven gravitational effects on the counterrotating eccentric weights,we prefer in many cases to orient their axes of rotation vertlcally, so.thatthe weights rotate in horizontal planes, subject to uniformgravitational elfects, to produce recipro pating forces longitudinallyof the conveying path and intermediate base. Such an arrangement isshown in Fig. 7 described below.

Fig. 4 illustrates schematically a somewhat modified arrangement of theinvention in which the spring beams of the lower or second set areessentially parallel to the spring beams of the upper set. Here theconveyor 1 20 is supported on the intermediate base 1'22 by upper springbeams 124 similar to those previously described. The intermediate basein turn is carried from a support 126 by lower inclined spring beams128. The support 126 in turn engages the building foundation 130. Thedesired force impulses are provided by an eccentric weight 132 rotatingon a transverse shaft 134 rotatably mounted in the intermediate base122.

In this case, the inclination of the lower spring beams parallel to theupper spring beams insures that the intermediate base member 122 hasfreedom of movement in the same direction as the upper conveying member120. Thus all force components and reactions perpendicular to the twosets of spring beams can theoretically be neutralized, subject to thelimitations previously expressed as to frictional and product damping,among other factors. In this construction also, the reactions due totorque involving the couple formed by the rotating unbalanced weight 132and the inertial reaction of the conveyor are transmitted through thelower spring beams 128 to the support 126 in foundation at reducedmagnitude. The reduction in magnitude of these forces is achieved inthis case by spacing the lower spring beams 128 farther apart than theupper spring beams 124 and substantially farther apart than the verticalor inclined length of the upper spring beams, i.e., farther apart thanthe lever arm of the above-described couple. The wider spacing betweenthe lower spring beams 128 effectively broadens the base or arm overwhich the force couple is transmitted and thus reduces the actual forcestransmitted at the ends of this longer arm.

A somewhat similar principle for the reduction of the forces transmittedto the foundation is illustrated in Fig. 5 Here the conveying member 136is supported on the intermediate base 138 by a first set of inclinedspring beams 140. The intermediate base 138 is then mounted in turn on alower support member 142 by means of substantially vertical spring beams144. The spring beams 144 are more widely spaced than the spring beamsof the upper set and thus have the effect previously described inconnection with Fig. 4. Furthermore, in the device of Fig. 5, thesupporting member 142 is extended longitudinally for a substantialdistance beyond the rest of the assembly and is provided with rigid feet146 engaging the floor or foundation of the building. The relativelygreat distance between these feet 146 further inmember to theintermediate base and on to the foundation or support, so that the twosets of spring beams previously discussed are provided byopposite endsof the same springs. In Fig. 6 the conveying member is located at 150,the intermediate base at 152, and the foundation at 154. Here, theintermediate base is above the conveyor and the point of ultimatesupport or foundation is above the intermediate base.-

Spring beams 156 are rigidly connected at their lower ends to theconveyor 150 and at their upper ends to the supporting foundation 154.At an intermediate point on these springs, which point may be verticallyadjustable, the intermediate base member, 152 is clamped as indicated at158. The desired force impulses are applied to the intermediate basemember by counterrotating weights 160 and 162 carried by parallel shafts164 and 166, respectively. The relative location of these shafts is suchthat the resulting force impulses indicated by arrow 168 are along aline perpendicular to the inclined spring beams 156.

Thus the lower ends of these spring beams 156 serve as the so-calledfirst set of spring beams previously discussed and provide the solesupporting connection between the conveying member and the intermediatebase. At the same time, the upper ends of springs 156 serve as thesecond set of spring beams previously discussed and provide the solesupporting connection between the intermediate base and the foundation.

Figs. 7 and show a preferred embodiment of the invention in which therelative vertical location and arrangement of the parts are againmodified. Here the conveying member 170 is relatively displaced abovethe intermediate base 172 and is connected thereto by inclined springbeams 174. The intermediate base 172 is in turn supported resilientlyfrom an overhead support or foundation 176 by means of a second set ofspring beams 178. Springs 178 are in this instance substantiallyvertical and are rigidly connected at least at one end as previouslydescribed. The use of the spring beams 178 provides the desired freedomof movement of the intermediate base in a substantially horizontaldirection, while at the same time these supports prevent Verticalrocking of the intermediate base as a result of the torques from theforce couple previously discussed.

A pair of counterrotating eccentric weights 189, carried by shafts 182,extending transversely of the intermediate base and direction of feed,provide the desired force impulses parallel to the intermediate base andto the direction of feed. In this case shafts 182 are vertical in orderthat weights 18 2 may rotate in a horizontal plane, subject to uniformgravity effect. The shafts 182 and weights 180 are mounted in a housing181 on frame 172 and driven by a suitable motor 183.

Example 1 As an example of one specific conveyor according to thepresent invention, a device of the general type shown schematically inFigure 7 was constructed as follows:

The first set ofjsprings 174 was placed at an angle of 27 degrees withthe vertical. A total of such springs was employed, the springs beingmade of an aluminum alloy, and the total K of these springs being 2930lbs. per inch.

For the second set of springs 173, 6 springs were used. These springswere made of /4 inch standard pipe and had a length of 54 inches,rigidly fixed at one end and semi-rigidly connected at the other end.The total K of these springs was not in excess of 560 lbs. per inch.

The mass of the intermediate frame 172 was substantially 485 lbs. andthe upper or conveying member was in the form of a tube having a mass ofapproximately 175 lbs.

For the force applying means two sets of oscillators were used, eachhaving two eccentric counterrotating weights of 11.96 lbs. effectiveweight 2.16 inches from their axes of rotation. They were rotated at-afrequency of substantially 770 r.p.m. In this particular case, the axesof the shafts were horizontal, instead of vertical (as shown in Fig. 7)and the two sets of oscillators were spaced slightly longitudinally ofthe intermediate base and driven by a single motor through suitablebelting.

The conveyor was operated successfully to convey precooked oat cerealrings.

As an example of another specific conveyor according to the presentinvention, a device of the general type shown schematically in Figure 7was constructed as follows:

The upper springs 174 were placed at an. angle of 27 degrees with thevertical. A total of 8 such springs were employed, the springs beingmade of an aluminum alloy known commercially as 248T aluminum and havinga length of 20 inches, a width of substantially 2 inches and a maximumthickness of /8 inch, the total K of the springs being 1160 lbs. perinch.

For the lower set of spring beams 178, 6 springs were used. Thesesprings were made of 1% inches standard pipe and had an average lengthof 40 inches connected at one end to a resilient mount fastened to theceiling. The total K of these resiliently mounted spring beams wasapproximately 300 lbs. per inch.

The mass of the intermediate base or frame 172 was substantially 145lbs. and the upper or conveying member was in the form of a tube havinga mass of approximately lbs.

For the force applying means, two eccentric counterrotating weights wereused, each of 11.96 lbs. effective weight at 2.16 inches radii. Theseweights were rotated on transverse shafts at a frequency ofsubstantially 670 rpm.

This conveyor was operated successfully to convey puffed corn cerealpellets.

According to the foregoing description, certain embodiments of theinvention have been disclosed which provide for the eifective vibratoryconveying of materials with reduction of the forces transmitted to thefoundation or other support on which the conveyor is mounted. The use ofa two-mass, two-spring system in which the conveying member is carriedfrom an intermediate base by inclined spring beams and in which cyclicalor reciprocating forces are applied only to the intermediate base (at afrequency approximating the natural frequency of the system involvingthe conveying member and its attached spring beams) provides the basicarrangement for theoretical elimination of movement of the intermediatebase and consequent reduction of force transmissions to the foundation.

In practice, however, we have found that such a system must be combinedwith substantially non-extensible spring beams as the means of supportfor the intermediate ,base, such beams having the direction andorientation previously discussed. Thus we have made it possible for thefirst time to provide effective conveying action with such a system byelimination of any rocking of the intermediate base due to transmissionof torques or force couples afiecting the system. Finally, theelimination of undesired force components in directions parallel to theinclined spring beams which carry the conveying member, by use of someforce-applyingmeans wlr ch provides reciprocating forces solely in alongitudinal direction within the specified range between linesperpendicular to the upper set of spring beams and lines parallel to theintermediate base, makes it possible to reduce further the transmissionof forces to the support or foundation and at the same time maintain ahigh degree of conveying efficiency.

Since minor variations and changes in the exact details of constructionwill be apparent to persons skilled in this field, it is intended thatthis invention shall cover all such changes and modifications as fallwithin the spirit and scope of the attached claims.

We claim:

1. A vibratory conveyor comprising a conveying member extending along apredetermined direction of feed, an intermediate base member displacedtherefrom and extending along a similar direction, a first set of springbeams similarly inclined with respect to the direction of feed on theconveying member and having their opposite ends connected to saidconveying member and base member at points spaced longitudinally alongthe directionof feed thereon respectively, said first spring beams eachbeing slightly inclined to a plane perpendicular to the direction offeed at the point of attachment of that spring .beam to the conveyingmember, said first spring beams providing the sole load-supportingconnection for said conveying member and permitting back and forthmovement along an inclined path perpendicular to said beams, a secondset of beams extending from said base member at points spacedlongitudinally along the direction of feed thereon, said second beamseach extending in a direction within the range of 45 from a verticalline and also within 45 of a line extending in the direction ofinclination of said first spring beams, said second beams beingconnected for resilient movement of the intermediate base along a lineperpendicular to said second beams and providing the sole connectionbetween said base member and a suitable support, and means applying acyclical force solely to said base member at a frequency relativelyclose to the natural frequency of the system consisting of the conveyingmember and first set of spring beams, said cyclical force includingmajor to and fro components along said path.

2. A vibratory conveyor according to claim 1 in which said forceapplying means has a construction and orientation applying to the basemember a reciprocating force which alternates rapidly in oppositedirections along a line which is perpendicular to the spring beams ofone of said sets at the point of application of said force.

3. A vibratory conveyor according to claim 1 in which said forceapplying means includes a pair of counterrotating eccentric weightshaving their rotational axes extending horizontally and transversely ofsaid path and base, said weights thereby providing a resultant forcewhich reciprocates parallel to said path and substantially perpendicularto said first spring beams.

4. A vibratory conveyor comprising a generally horizontal,longitudinally extending conveying member, an intermediate base membersubstantially parallel thereto and vertically displaced therefrom, afirst set of parallel spring beams slightly inclined to the vertical andhaving their opposite ends rigidly connected to said conveying memberand base member at longitudinally spaced points thereon respectively,said first spring beams providing the sole load supporting connectionfor said conveying member and permitting back and forth movement alongan inclined path perpendicular to said beams, a second set of parallelspring beams extending from said base memher at longitudinally spacedpoints thereon in a direction within the range limited on the one handby lines parallel to said first spring beams and on the other hand bysubstantially vertical lines, said second spring beams providing thesole connecting means between said base member and a suitable stationarysupport, and means applying a cylical force solely to said base memberat a frequency relatively close to the natural frequency of the systemconsisting of the conveying member and first set of spring beams, saidcyclical force including major to and fro components along said path.

5. A vibratory conveyor comprising a conveying member extendinglongitudinally along a desired direction of feed, a base member parallelthereto, a first set of spring beams parallel to each other andconnecting the conveying member and base member at longitudinally spacedpoints thereon respectively, the individual spring beams normally lyingin planes which intersect at an acute angle a plane normal to thedirection of feed, the lines of intersection of such planes beinggenerally horizontal and said spring beams thereby providing forrelative back and forth movement of the conveying member along a pathperpendicular to the spring beams and vertically inclined with respectto the direction of feed, a second set of spring beams parallel to eachother and extending generally perpendicularly from said base member atlongitudinally spaced points thereon and constituting the soleconnection between said base and a suitable rigid support, and means forapplying to said base member a reciprocating force which alternatesrapidly in opposite directions along a line parallel to said path at afrequency subsubstantially equal to the natural frequency of the sys temconsisting of said first set of spring beams and said conveying member.

6. A vibratory conveyor according to claim 5 in which said conveyingmember is above said base member and the spring beams of said second setextend downwardly from said base member.

7. A vibratory conveyor according to claim 5 in which said conveyingmember is above said base member and the spring beams of said second setextend upwardly from said base member.

8. A vibratory conveyor according to claim 5 in which the spring beamsof said second set are parallel to the spring beams of the first set.

References Cited in the file of this patent UNITED STATES PATENTS2,353,492 OConnor July 11, 1944 FOREIGN PATENTS 584,435 Germany Sept.20, 1933 828,944 Germany Jan. 21, 1952

